The present disclosure relates to electrostatic latent image developing toners.
For energy saving and downsizing of image forming apparatuses, there is a demand for a toner excellent in low-temperature fixability. The use of a toner excellent in the low-temperature fixability enables the toner to be satisfactorily fixed on a recording medium even when the temperature of a fixing roller is low.
In order to obtain the toner excellent in the low-temperature fixability, a toner producing method has been proposed which uses a binder resin having a low melting point (or a binder resin having a low glass transition point) and a mold releasing agent having a low melting point. However, it is difficult to produce a toner excellent in high-temperature preservability by this method. The high-temperature preservability of a toner exhibits a property that toner particles contained in the toner are not aggregated even when the toner is stored under a high temperature environment. Toner particles of a toner poor in the high-temperature preservability are liable to aggregate under a high temperature environment. When the toner particles aggregate, the charge amount of the toner particles may be likely to decrease.
For purpose of improving the low-temperature fixability, high-temperature preservability, and blocking resistance of a toner, a toner containing toner particles each having a core-shell structure has been proposed.
In an exemplified toner containing toner particles each having a core-shell structure, a toner core contains a binder resin having a low melting point. Further, the toner core is coated with a shell layer made from a resin. In addition, the resin forming the shell layer has a higher glass transition point (Tg) than the binder resin contained in the toner core.
In another exemplified toner containing toner particles each having a core-shell structure, the surface of a toner core is coated with a thin film (shell layer) containing a thermosetting resin. The toner core has a softening point of 40° C. or more and 150° C. or less.